Heart no Diamond

Himeno feels pain in her chest whenever a boy touches her, because she has the Diamond of the Heart. Yet two boys from her childhood, the gentle Mamoru and the blunt Keigo, can touch her without hurting her. Unaware of the diamond within Himeno, both boys promised to protect her when they were young. Now that people threaten to take her heart, Mamoru and Keigo may have to keep that promise as her knights.